Need Help - Keep Losing Heat in 1 Zone

[ManiacPD]

I have a wood boiler with a 250 gallon propane storage tank that ties into my oil system. I'm currently burning wood so the oil burner motor is disconnected, but the circulators still run to pump heat to the house. The house is a cape (2 stories) with 4 zones - 1 for the boilermate (DHW), 1 for the 1st floor, 1 for the 2nd floor, and 1 for the bathrooms. The house has 3 bathrooms - 2 on the 1st floor and 1 on the 2nd floor, with the thermostat in one of the 1st floor bathrooms. I have circulators in a bank next to my oil burner that pull directly from the storage tank in the garage (40 feet away).

For some reason I keep losing heat in the bathroom loop. I have no problems with getting heat to the main floors, nor any issues making hot water. I burned wood from Labor Day until New Years when we went away. I changed back over to oil (turn 3 ball valves and energize oil burner motor) while we were gone, but since switching back to wood I have lost heat to the bathrooms 3 times.

When switching from wood to oil and back to wood I sometimes get a little air in one zone. I've bled all zones and haven't noticed any air coming out. Both times the bathrooms got cold I bled about 6-8 gallons from the bathroom zone and got my heat back. My wife just called and it is out again.

From what I can tell the circulator is working fine. System pressure runs 12-15 psi from cold (110F) to hot (210F) as I have 40+ gallons of expansion capacity.

Does anyone have any ideas why I keep losing heat in this one zone? Your thoughts and suggestions are appreciated.

Thanks in advance!

 

[maple1]

Does each zone have its own zone valve & circ? Or something else?

My zone valves have switches in them - when the thermostat calls for heat, it opens the valve which in turn closes the internal switch which then starts the circ. These switches go bad quite frequently. If a switch goes bad, the valve will open but it won't start the circ. I think right now I have at least one bad switch in one of my 4 zone valves, but haven't bothered changing it yet since I only have one circ, and as long as one of the good valve switches is calling for heat, the water circulates wherever there is an open zone valve.

Usually I would suspect air getting in though - more troubleshooting might be needed, like turning on only that zone and tracing where the heat is going by feeling the pipes or using an IR gun (although they don't work good at all on bare copper) - and making sure that turning on just that one zone does in fact start the circ.

 

[mikefrommaine]

Id guess you still have air in the loop. Try bleeding it again.

 

[ManiacPD]

Thanks for your reply Maple.

To answer your question each zone has it's own circulator. There are no zone valves in the system, only circulators.

I did exactly as you suggested and turned the heat back on the other three zones, leaving only the bathroom zone running. The bathroom circulator motor is humming and is very warm to the touch but the pipes above and below it are not hot at all, indicating no water flow through the loop. I then turned up the knob on the boilermate (DHW maker) to start the circulator and held my hand on the supply pipe and it became very hot within a few seconds, just to verify the system is working. Soon after the return got hot as well, as the hot water made it through the loop.

 

[ManiacPD]

Id guess you still have air in the loop. Try bleeding it again.

Ordinarily I'd agree with you Mike but I've purged at least 2-3 times the amount of water in the zone on two separate occasions already and it only helps temporarily. What baffles me is there is no air coming out...usually the hose will belch air and water as the air comes out but it's just nice, smooth, consistent flow as I fill up two 5-gallon buckets.

 

[maple1]

You might have a bad circ - I'm thinking that if the pipes on either side of it are not hot, it shouldn't be either?

Is there a cover over a shaft you can pop off & see if the shaft is turning?

 

[Clarkbug]

I agree with maple, that perhaps your circ is going bad.

Also, you said your pressures start at 12 and go up to 15 when hot? I would put some more pressure in your system. That would help any air that may still be in your system purge out.

Do you have isolation valves on your circs? If so, can you swap one from one of the zones to the bathroom zone and see if the problem moves with the circ?

 

[maple1]

Not sure what kind of circs you have or other related details - but what stops the zone(s) from circulating by convection when it is not calling for heat?

 

[ManiacPD]

I forgot I had pictures on my work computer and found this one showing the circulator bank...I'm wondering if the flow control at the top of the picture may be sticking in the closed position, which would intermittently stop the flow???

 

[ManiacPD]

Not sure what kind of circs you have or other related details - but what stops the zone(s) from circulating by convection when it is not calling for heat?

See my picture. I'll check when I get home.

 

[mikefrommaine]

- but what stops the zone(s) from circulating by convection when it is not calling for heat?

See my picture. I'll check when I get home.

In the top of the pic it looks like he has taco sweat checks.

 

[ISeeDeadBTUs]

switch the questionable pump with the 2nd floor one assuming they are the same. Re-bleed, see which zone dies.

Does your system pull from storage when yer on oil?
Does heat return to that zone if you return to oil?

 

[ManiacPD]

switch the questionable pump with the 2nd floor one assuming they are the same. Re-bleed, see which zone dies.

Does your system pull from storage when yer on oil?
Does heat return to that zone if you return to oil?

My wife just called and the tank is now hot (180F) and she has heat in the bathrooms. I asked her if she was in the outhouse or the bathroom when she called earlier to complain of no heat. For some reason she didn't think that was funny.

When burning oil the wood boiler and storage tank are isolated from the oil system. The thought of back-heating 300 gallons of water and associated steel pressure vessels with oil is a scary proposition.